1. Field of Invention
The present invention relates to an apparatus for semiconductor fabrication. More particularly, the present invention relates to an apparatus for immersion lithography.
2. Description of Related Art
Lithography process is one of the most important processes of semiconductor fabrication. Lithography process uses light to transfer geometric patterns from a mask to a light-sensitive chemical such as photoresist on a substrate of a wafer. A series of chemical treatments then engrave the exposure pattern on the wafer underneath the photoresist layer to form microstructures or transistors.
Conventionally, a photolithography process is carried out under normal incidence, which means that the principal plane of the photoresist layer to be photo-structured is about perpendicular to the main direction of a light beam. However, it is hard to produce three-dimensional micro-structures with inclined flanks by using the conventional photolithography apparatus.
Therefore, a new apparatus for performing lithography with normal and inclined incidence is needed. The apparatus may control the inclined angle precisely to ensure the inclined flanks of the three-dimensional micro-structures.